1. Field of the Invention
The present invention relates to a cross-linear slide bearing for use in an X-Y table which is capable of linearly sliding an object to be slid in directions crossing each other.
2. Description of the Prior Art
The above-described cross-linear slide bearing is employed to linearly slide a table having an object to be slid (for example, a machine tool) mounted thereon in directions which are orthogonal to each other and to accurately move such object to a predetermined position within a given plane.
An example of a conventional bearing of the type described above is mentioned in the specification of Japanese Patent Publication No. 32,888/1979. The conventional cross-linear slide bearing is arranged as follows: A thick-walled bearing body is provided on the upper and lower surfaces thereof with recesses for respectively receiving track rails, the recesses extending in directions crossing each other. Each track rail is provided on each of the shoulder portions thereof with two loaded ball rolling grooves extending longitudinally. Further, each of the recesses for receiving the track rails is fitted therein with a multiplicity of loaded balls which roll along the loaded ball rolling grooves, the balls being allowed to recirculate in two rows on each of the right and left sides of the recess.
The above-described conventional cross-linear slide bearing, however, encounters the following problems: Since the bearing body has a large wall thickness and moreover it is fitted at its upper and lower surfaces with the track rails, the apparatus as a whole is unfavorably increased in height. Consequently, when the bearing is incorporated in an X-Y table, there is a need for an inconveniently large mounting space in the vertical direction, and it is not possible to obtain a satisfactory stability. Further, since four rows of loaded balls roll and recirculate within each recess, it is disadvantageously necessary to reduce the radius of curvature of a ball turning portion at each of the longitudinal ends of the loaded ball rolling passages, which makes it difficult for the balls to roll smoothly. In addition, since the loaded ball rolling passages are cut inside the recess in order to fit the ball therein, an inconveniently large amount of labor is required for machining and assembling operations, resulting in an increase in production cost. Furthermore, since the bearing body has a large wall thickness, the weight of the bearing as a whole is increased correspondingly, which disadvantageously involves a correspondingly large inertia force.